1. Field of the Invention
The present invention relates to wireless terminals with radio reception capability.
2. Description of the Related Art
The Radio Data System (RDS) protocol includes information about Program Service (PS), Radio Text (RT) as additional data information for a channel provided by a broadcasting station, Alternative Frequency (AF), etc. Among these, the AF service provides a user with a frequency of another channel transmitting the same broadcast as that carried by a currently received channel when the reception state of the current channel is poor, thereby providing seamless radio service to the user.
The AF service checks the reception state of a currently used channel for a predetermined time, and if the state of the current channel is poor, the AF service searches an AF candidate channel list. If an AF candidate channel is the same broadcasting channel as the current channel, a switch over is made to the AF candidate channel, such that the AF service is completed.
To execute the AF service, first, a measurement for checking the reception state of the current channel is required. When the reception state of the current channel is inadequate for a predetermined time, that is, during a tolerance period, the AF candidate channel list is searched. The smaller the tolerance period, the more sensitive is the receiver to an instantaneous change of the reception state in a channel.
During a process of searching the AF candidate channel list, a radio mute condition inevitably occurs, such that muting more frequently occurs with a smaller tolerance period. In other words, as the AF service is provided with more sensitivity, the user experiences more instances of muting due to frequent AF attempts.
Generally, the AF service is a useful service for a user's driving conditions, but recently, the AF service has been needed also for walking conditions. In the context of driving, an RDS reception state is typically good and a channel reception state progressively changes, such that a relatively large tolerance period (e.g., 40-60 seconds) is used.
On the other hand, in the context of walking, an instantaneous electric field change frequently occurs, and in any given region, electric field conditions may be poor. As a result, in walking conditions, the use of a small tolerance period is required for sensitivity to the instantaneous electric field change. When the AF service is provided with high sensitivity, however, a side effect of frequent occurrence of muting is generated.